docs(FN-1158): add comprehensive project documentation suite

- Add docs index with structured navigation and links across the new documentation set
- Document onboarding and technical foundations with getting-started and architecture guides
- Add detailed CLI and settings references plus feature guides for dashboard, tasks, workflow steps, missions, multi-project, and agents
- Add a contributing guide and polish cross-references between docs pages for discoverability
- Include dashboard screenshots for key views to provide visual context in the guides

docs/dashboard-guide.md

@@ -0,0 +1,156 @@
+# Dashboard Guide
+
+[← Docs index](./README.md)
+
+The Fusion dashboard is the main control plane for tasks, agents, missions, settings, logs, and repository operations.
+
+## Board View
+
+Board view is the kanban surface for day-to-day operation.
+
+Features:
+
+- Drag-and-drop between lifecycle columns
+- Search/filter tasks
+- Column visibility controls
+- Inline quick entry creation
+- PR/issue badges with live updates
+
+![Board view](./screenshots/dashboard-overview.png)
+
+## List View
+
+List view is optimized for dense task management.
+
+Features:
+
+- Grouping modes (for example by column/size)
+- Inline title editing
+- Duplicate task actions
+- Quick scanning of metadata without card expansion
+
+## Interactive Terminal
+
+Fusion embeds a terminal using xterm.js.
+
+Features:
+
+- Multiple terminal tabs
+- PTY-backed shell sessions
+- Mobile-aware virtual keyboard handling and auto-refit behavior
+
+![Interactive terminal](./screenshots/terminal.png)
+
+## Git Manager
+
+Git manager centralizes repo operations in the dashboard.
+
+Features:
+
+- Branch/worktree visibility
+- Commit and diff browsing
+- Push/pull/fetch actions
+- Remote editing controls
+
+![Git manager](./screenshots/git-manager.png)
+
+## File Browser and Editor
+
+Built-in file tools allow quick inspection and edits.
+
+Features:
+
+- Browse project root and task worktrees
+- Open files in an editor with syntax highlighting
+- Navigate artifacts generated during task execution
+
+## Activity Log
+
+The activity log tracks task/system events over time.
+
+Features:
+
+- Event type filtering
+- Auto-refresh updates
+- Operational traceability for task moves, merges, settings updates, and errors
+
+## Theme System
+
+Visual customization includes:
+
+- Theme mode: dark/light/system
+- **30 color themes** (including Ocean, Forest, Nord, Dracula, Gruvbox, Tokyo Night, and more)
+
+Theme preferences are stored in global settings.
+
+## Usage Dialog
+
+Usage view shows provider consumption and limits.
+
+Features:
+
+- Progress bars by provider/model
+- Reset window visibility
+- Helps diagnose capacity/rate-limit conditions
+
+## Spec Editor
+
+The spec editor lets you edit `PROMPT.md` directly.
+
+Features:
+
+- Manual prompt edits
+- AI revision requests
+- Rebuild/regenerate flows when task intent changes
+
+## Planning Mode
+
+Planning mode is an AI interview workflow for shaping task scope.
+
+Features:
+
+- Clarification Q&A
+- Summary generation
+- Two final actions: **Create Task** or **Break into Tasks**
+- Multi-task creation uses key deliverables and dependency linking
+
+## Subtask Breakdown Dialog
+
+The subtask dialog supports structured decomposition before creation.
+
+Features:
+
+- AI-generated subtasks
+- Drag-and-drop reordering
+- Keyboard reordering controls
+- Dependency linking constrained to earlier items
+
+## Settings Modal
+
+Central place for model/provider config, execution behavior, notifications, backups, and UI preferences.
+
+![Settings modal](./screenshots/settings.png)
+
+## Workflow Step Manager
+
+Create and manage reusable quality gates for tasks.
+
+![Workflow step manager](./screenshots/workflow-steps.png)
+
+## Agents View
+
+Inspect agents, runtime status, run history, and configuration.
+
+![Agents view](./screenshots/agents-view.png)
+
+## Mission Manager
+
+Manage mission hierarchy and progression state.
+
+![Mission manager](./screenshots/mission-manager.png)
+
+## Task Detail Modal
+
+Inspect logs, step progress, workflow outcomes, and model overrides.
+
+![Task detail modal](./screenshots/task-detail.png)